`c_uint` changed from 16-bit to 32-bit

[mlund]

core::mem::size_of::<core::ffi::c_uint>() == 2 used to be true, but it is now a 32-bit integer, likely carried over from the host system. The symptom appear in mrkits/rust-mos:13f2838f9-334fc98-8f3a80f8 arm64 build. The installed clang compilers correctly reports 16-bit with e.g. mos-mega65-clang -dM -E - < /dev/null | grep __SIZEOF.